My familiarity with it is superficial and only as an iPhone user, it is not an API I have ever concerned myself with, so first, I might be wrong about this next part but second, my understanding is that it provides almost nothing about you except a number or a string. I’ve never delved into Apple’s docs to find out because the “how they do it” has always been less important to me than the “how do I turn this off”.
If you go into Settings on iOS 13/iPadOS 13 and into the Privacy pane, all the way at the bottom you should see two tabs, one labeled “Analytics & Improvements” which is for information Apple collects for the device, Siri and iCloud, and another “Advertising”.
It’s in that second one that you can toggle “Limit Ad Tracking”, off by default today, on by default in iOS 14, at least that’s the plan and is the case in reports from people using the beta releases. Right below this toggle is a button labeled “Reset Advertising Identifier” which does exactly what it says. This is the “IDFA” that is the subject of discussion and will be the same value returned to Apps that request to use it. If you reset it, that will break continuity with your previous identifier, at least in theory.
If you go into Settings on iOS 13/iPadOS 13 and into the Privacy pane, all the way at the bottom you should see two tabs, one labeled “Analytics & Improvements” which is for information Apple collects for the device, Siri and iCloud, and another “Advertising”.
It’s in that second one that you can toggle “Limit Ad Tracking”, off by default today, on by default in iOS 14, at least that’s the plan and is the case in reports from people using the beta releases. Right below this toggle is a button labeled “Reset Advertising Identifier” which does exactly what it says. This is the “IDFA” that is the subject of discussion and will be the same value returned to Apps that request to use it. If you reset it, that will break continuity with your previous identifier, at least in theory.